Dr. Victor Falco, later known as The Rat King, was a sleazy scientist who used his knowledge and talents for his own selfish gain. After an accident involving a fire, mutagen, and a chemical he was developing to give him telepathic powers, he became this series' incarnation of the Rat King.
As a normal human, Falco wore a white lab coat, had gray hair with white markings, brown shirt and pants, and a tie.
As the Rat King, his skin is pale green, his eyes glow red, he resembles a corpse, his teeth are rotten, he wears wraps on his arms and legs, he has a black coat and hat, his hair is messy and he wears a blindfold at time.
Rat King started out as a human scientist named "Dr. Victor Falco", and he debuted in the episode Monkey Brains. He and his colleague Dr. Tyler Rockwell were working on an experiment that involved mutagen, a neurochemical, and monkey DNA when they were approached by the Kraang. When it was mentioned on the news that Dr. Rockwell was missing, Dr. Falco alluded that he was oblivious to the situation.
Falco pretended to help April O'Neil and the Ninja Turtles—and gained their sincere trust. The Turtles later figured out what Dr. Falco was really doing; experimenting with mutagen on his former colleague, Dr. Rockwell, turning the latter into a mutant monkey with the mutagen. Falco gained the same psychic powers temporarily by extracting a neurochemical from the mutant's brain and injecting himself with it. With his new power, Falco was able to defeat the Turtles in combat by reading their thoughts and predicting their every move. Donatello finally defeated him by fighting without thinking, but Falco escaped before the Turtles could ask him what he knew about the Kraang.
In I, Monster, Falco was shown living in hiding, and continued to work on his psychic neurochemical in a secret laboratory, with only sewer rats to experiment on. One day, the rats chewed through some cables and started a fire in the lab. Falco was injured by the flames, but the neurochemical splattered on him, granting him a psychic connection to rats. Falco used his new ability to control the rats in his lab and they saved him from the fire. Some time later, Falco went into hiding in the sewers, nicknamed himself as The Rat King, and began plotting to use his powers to take over New York City. He launched a full scale assault on the city with his hordes of rats. Eventually, Rat King became aware of Splinter through telepathy. Knowing that the Turtles would come to stop him, The Rat King used psychological warfare to control Splinter's mind. When Splinter fights the Turtles, they are overconfident because they were actually able to land a blow on him (though they lost soon after), but soon realize that Splinter was going easy on them all of those years. They manage to snap him out of it and Splinter defeats The Rat King with nothing but two fingers. Rat King was last seen being carried off by his rats. He is still alive...
In Of Rats and Men, the Rat King returned, first reaching into Splinters mind to both torment him, but also learn about the mutagen to create more like him, as well as sending giant mutated Rats to gather humans to be test subjects, in the end while fighting Splinter, Splinter knocks away one of the Rat kings rats then blindfolds himself, rendering the Rat king blind, who kept swatting at Splinter, only to fall in a bottomless void.
In Darkest Plight, after Splinter fell into the darkness of the Undercity during a fight with Super Shredder, he found his body battered and a leg broken. At the pit's bottom, he encountered the Rat King once again, his visage having gone pale, but still active enough to torment Splinter. Rat King attempted to subjugate Splinter, playing mind games with him, coercing him into eating a rat (which he refused), and attacking the ninja as a golem made of rats. Splinter eventually succumbed to his rat nature under the king's influence, but after seeing a vision of his sons and Tang Shen, he fought back and defeated Rat King. He then found Falco's skeletal remains lying splayed on the ground, revealing that he really had died following his defeat at Splinter's hands, and that what he saw was all a hallucination from his fever.
Powers and Abilities
In Monkey Brains, Falco (after gaining the neurochemical DNA from Rockwell and injecting it into his own mind), had the ability to read minds and uses it to stop anyone. This is observed when he read the Turtles' thoughts and was able to defeat them in combat (except for Donatello, who was eventually able to defeat Falco without thinking at all). After his mutation, however, he was only able to enter the minds of rats.
Like previous versions of the character, Rat King has psychic control over rats, being able to precisely command single individuals and large swarms. His powers were even able to control Splinter's mind, but Splinter was able to fight it. He was also blinded during the accident in his lab, so he often kept his own eyes covered with one large band. However, it has been shown that his powers allow him to see through the eyes of rats in his vicinity, both negating the need for his own eyes and making any single rat a potential spy, however as shown in "Of Rats and Men, this can be negated if all nearby rats are unable to see themselves.
Falco was nothing short of a power-mad psychopath who was only concerned about his own goals. His psychopathic tendencies were nearly invisible due to his metaphorical mask of normalcy, he was a talented liar, a deceitfully cunning mind who was able to fool April, Donatello and the entirety of New York into thinking he had no idea of his friend, Doctor Rockwell's disappearance. Falco was immoral, ruthless and arrogant and so uncaring that he was capable of kidnapping and mutating his colleague so he could perfect a psychic serum.
Falco was massively sadistic taking joy in seeing Rockwell's pain and during his fight with Donatello cruelly mocked him over his romantic feelings for April.
Although in his past experiences he has had at least some, but granted very small level of decency after being mutated while trying to recreate his psychic serum and is granted a telepathic connection to rats. Granting himself the title of The Rat King, Falco was a fully fledged misanthrope who began to see humanity as nothing more than an infestation and as such took satisfaction in terrorizing New York, he would either mutate or kill any human in his path. Ironically Falco's archenemy is the same person he thought was also his equal, Hamato Yoshi who he tried to mind-control but in the end Splinter was able to kill him.
Falco completely valued rat life and was left screaming in rage when Splinter had kicked his pet rat and friend, Aristotle over a ledge.
The Rat King has a white rat, most often sitting on his shoulders, since the Rat King is blind but can see through rat's eyes Aristotle allows his to see an opponent right next to him and to fight him himself, as seen in Of Rats and Men. He is named after the Greek philosopher Aristotle (Ἀριστοτέλης) whose name means "the best purpose". The Rat King has also given names to a few of his Giant Rats.
- Victor Falco is extremely similar to the H.P. Lovecraft character Herbert West, who was portrayed by Falco's voice actor, Jeffrey Combs in the "Re-Animator" film series. West was a scientist who experimented with a green substance similar in appearance (but not in effect) to the Ooze. As the Rat King, his appearance somewhat resembles the appearance of Scarecrow from The New Batman Adventures (1997), who Combs also voiced.
- The Rat King's outfit (long black coat and black wide-brimmed hat) is nearly identical to the standard outfit worn by medieval plague doctors. This is noteworthy in that the Bubonic plague was spread by fleas being carried by rats.
- Michelangelo was extremely annoyed that the Rat King nicknamed himself, as he's the one who usually comes up with the nicknames. He tried numerous alternatives: Lord Rattington, Count Ratula, Verminator, etc. until he begrudgingly accepts it.
- One of Michelangelo's suggested nicknames, Verminator, is also the name of another TMNT character, Verminator-X.
- Rat King is the name of a phenomena in which many rats get stuck together by their tails.
- Several of the Rat King's giant mutant rats from the episode Of Rats and Men were named after Roman emperors as Caligula, Claudius, Nero and Commodus.
- Victor Falco is also reminiscent of Dr. Victor Feral from Teenage Mutant Ninja Turtles & Other Strangeness. Like Dr. Falco, Doc Feral is a kind-acting human scientist who secretly performs unethical mutagenic experiments involving animals (as Falco did to Dr. Rockwell), and keeps mutant rats as friends or servants (as does the Rat King).